Influences of frequency on nitrogen fixation of dielectric barrier discharge in air

The influences of frequency on nitrogen fixation of dielectric barrier discharge in air were studied by electrical diagnostics, gas detection and infrared detection methods. The system power, nitrogen oxide concentration, voltage-current waveform, dielectric surface temperature distribution and filamentous discharge pictures were measured, and then the energy yield was calculated; paper studied their changing tendencies in the presence of frequency. Results show that frequency has strong influences on nitrogen fixation. When the parameters of reaction chamber and amplitude of applied voltage is fixed, with the increasing of frequency, the system power increases; in 5-10 kHz, nitrogen oxide gas concentration up to 1113.7 mg m-3, and 7 kHz is the optimal nitrogen fixation frequency whose energy yield is 20.5 mR （m3 W）-1.

从地理位置、国力、战争角度论西夏与蒙古的关系

本文从地理位置、国力、战争角度对西夏王朝与蒙古国的关系进行深入研究，挖掘西夏与蒙古的成败，探寻乱世之中两个大国的不同与相同，从而对那段时期的历史有更深刻的了解，并获得自己的收获和教训。

故宫的走兽与建筑等级的关系——北京大学附属中学初中综合实践课

本文是以故宫太和殿屋檐上的走兽为代表,来探究走兽的作用及与建筑等级的关系。主要内容包括:1、对走兽的基本资料进行分析,了解各方面的情况,并进行初步的预测与实施。2、通过拍摄的照片与查找到的资料作对比,核实该资料是否属实。3、通过书籍、网络等渠道,了解到更多关于走兽的资料,并进行分析,思考走兽的作用及与建筑等级的关系。本课题研究,使我们对走兽有了更深一步的了解,从而激起了我们对建筑浓厚的兴趣,对今后的学习专业选择及学术知识都有很大帮助;而且帮助我们全方面了解中国古代皇家建筑的内在建筑意义,以及走兽与建筑等级的关系,而不是只停留于观赏其表面的雍容华贵。